High Néel temperature and magnetism modulation in 2D pentagon-based XN2 (X = B, Al, and Ga) structures with spin-polarized non-metallic atoms

Abstract

Magnetic semiconductors with spin-polarized non-metallic atoms are usually overlooked in applications because of their poor performances in magnetic moments and under critical temperatures. Herein, magnetic characteristics of 2D pentagon-based XN₂ (X = B, Al, and Ga) are revealed based on first-principles calculations. It was proven that XN₂ structures are antiferromagnetic semiconductors with bandgaps of 2.15 eV, 2.42 eV and 2.16 eV for X = B, Al, and Ga, respectively. Through analysis of spin density distributions and molecular orbitals, the magnetic origin was found to be located at the antibonding orbitals (π*2p_x and π*2p_z) of covalently bonded N atoms. Furthermore, it was demonstrated that XN₂ semiconductors exhibit Néel temperatures (T_N) of as high as 136 K, 266 K and 477 K, as found through Monte Carlo (MC) simulations of the Ising model. More significantly, the phase transition of the magnetic ground state from antiferromagnetic order to ferromagnetic order, continuous distribution of bandgaps from 2.0 eV to 2.5 eV, and enhancement of magnetic moment from 0.3μ_B to 1.2μ_B could be realized by exerting external fields. Our work proposes a novel spin-polarized phenomenon based on covalent bonds, ameliorating the performances of magnetic semiconductors with spin-polarized p-orbit electrons and providing immense application potentials for XN₂ in spintronic devices.